On a relatively small screen, in a conference room or classroom, the speaker easily points to areas on the screen with the aid of a pointer stick. The use of larger projection screens requires the speaker to use a laser pointer or to advance into the projected scene to point to various elements.
Many a speaker having entered into the scene would like to turn and look directly at his audience as he speaks. Unfortunately, being in the projection beam, he is blinded by the projector and cannot see his audience. Furthermore, the scene with its text and graphics, is projected onto the speaker, which is quite distracting to an audience.
A video projector shows the desired scene on a projection screen. An infrared source close to the video projector uniformly floods the projection screen with non-visible infrared radiation. An infrared sensitive camera, also close to the video projector, observes the projection screen and sees only the uniform infrared illumination of the screen. Upon entry of a subject into the projected video image, the infrared reflected from the subject will not match that of the projection screen and thus the subject area is identified. All pixels of the projected scene, in the area occupied by the subject, are inhibited before reaching the video projector. The subject may then look directly at an audience without being blinded by the projector.